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Many land uses are highly prone to invasion of new non-native plant species under changing climate. Identification of suitable habitat for invasive weeds and their projected infestation extent across different land use cover types under a changing climate is crucial for the broad management goals of prevention, detection, and rapid response. In this study, we adopted an ensemble approach of species distribution models to project potential habitat of the invasive annual grass, Ventenata dubia, along the road corridor of Gallatin county, Montana, USA, under current and future climates. The model prediction of V. dubia habitat was excellent. The climate predictors most correlated with V. dubia occurrence were precipitation, potential evapo-transpiration, relative humidity, vapor pressure deficit, and solar radiation for months during the growing season, and fall germination. The model projected 1,945 and 7,374 km2 under RCP4.5, and 2,306 and 11,050 km2 for road corridors and Gallatin county, respectively. We found that the projected increases in V. dubia infestations were highest for road corridors (239% under RCP4.5 and 302% under RCP8.5) compared to that of Gallatin County (127% under RCP4.5 and 241% under RCP8.5). Among the land class types, the model projected greatest expansion of V. dubia cover across agriculture land with 425% and 484% and grassland with 278% and 442% increase under RCP4.5 and RCP8.5, respectively. We conclude that V. dubia with a short history of invasion is expanding at an alarming rate challenging the status quo and requires greater investment in detection and monitoring to prevent further expansion.
Arjun Adhikari; Jane Mangold; Lisa J. Rew. Climate Change and More Disturbed Land-Use Types will Further the Invasion of a Non-Native Annual Grass, Ventenata Dubia. 2021, 1 .
AMA StyleArjun Adhikari, Jane Mangold, Lisa J. Rew. Climate Change and More Disturbed Land-Use Types will Further the Invasion of a Non-Native Annual Grass, Ventenata Dubia. . 2021; ():1.
Chicago/Turabian StyleArjun Adhikari; Jane Mangold; Lisa J. Rew. 2021. "Climate Change and More Disturbed Land-Use Types will Further the Invasion of a Non-Native Annual Grass, Ventenata Dubia." , no. : 1.
The productivity of herbaceous and understory woody vegetation is critical for wildlife habitat, livestock forage, and biodiversity, and is influenced by both annual weather patterns and tree dominance. With the goals to inform management and understand climate change implications, we determined the effects of tree harvest, prescribed fire, and 31 yr of climate variability on understory aboveground net primary productivity (ANPP) for ecosystems ranging from mature forest to grassland in a long-term study in southeastern Oklahoma, USA. In 1984, starting with a mature forest dominated by Pinus echinata and Quercus stellata, replicated experimental units were created by various combinations of pine harvest, hardwood thinning, and subsequent fire return intervals (1–4 yr and none). Understory ANPP (forbs, grasses, and woody plants) was measured by clip plots at the end of each growing season. Stepwise regression models were developed between understory ANPP and tree basal area, litter accumulation, fire return interval, and monthly, seasonal, and annual weather variables. Understory ANPP was dominated by grasses and ranged from 27 g·m−2·yr−1 for the mature forest to 374 g·m−2·yr−1 for an annually burned grassland/savanna. In general, herbaceous ANPP was inversely related to tree dominance (basal area), litter accumulation, and early and late growing season temperatures, and positively related to June precipitation. Understory woody ANPP was influenced by tree basal area, positively influenced by precipitation, and negatively influenced by summer soil moisture deficits. Our results indicate that prescribed fire, through its negative influence on tree basal area and litter accumulation, is critical to maintaining highly productive understories and that a three-year return interval is a threshold to stall redevelopment of forest. For herbaceous ANPP, timing of precipitation, especially mid-growing season, appears more important than total precipitation, and higher temperatures within the range our site experienced did not have a large negative effect. In contrast, understory woody ANPP was negatively influenced by drought indicating climate change may have variable effects on different functional groups.
Arjun Adhikari; Ronald E. Masters; Kumar P. Mainali; Chris B. Zou; Omkar Joshi; Rodney E. Will. Management and climate variability effects on understory productivity of forest and savanna ecosystems in Oklahoma, USA. Ecosphere 2021, 12, e03576 .
AMA StyleArjun Adhikari, Ronald E. Masters, Kumar P. Mainali, Chris B. Zou, Omkar Joshi, Rodney E. Will. Management and climate variability effects on understory productivity of forest and savanna ecosystems in Oklahoma, USA. Ecosphere. 2021; 12 (6):e03576.
Chicago/Turabian StyleArjun Adhikari; Ronald E. Masters; Kumar P. Mainali; Chris B. Zou; Omkar Joshi; Rodney E. Will. 2021. "Management and climate variability effects on understory productivity of forest and savanna ecosystems in Oklahoma, USA." Ecosphere 12, no. 6: e03576.
We investigated the radial growth response of shortleaf pine (Pinus echinata) to climatic variation and management using tree cores collected in southeastern Oklahoma at the drier, western limit of its range. Beginning in 1984, experimental units were created by various combinations of pine harvest, hardwood thinning, and fire return intervals (1, 2, 3, 4 years and none) that produced ecosystems ranging from mature, closed canopy forest to open savanna. Monthly and seasonal weather for previous- and current-year as well as growing seasons since fire were used to determine the relationship between radial growth and climate variability (1987–2018) for different management regimes. Across all treatments, growing season precipitation (~5% decrease per 100 mm decrease in precipitation), average summer temperature maximum (~7% decrease with 1 °C increase), and previous year’s average October minimum temperature (~6% increase per 1 °C increase) were the variables most frequently correlated with variation in ring width. Annual wood and latewood growth increments were correlated (R2 = 0.60) and generally responded similarly to climate variability, with latewood more sensitive to late growing season conditions. Management with frequent fire that resulted in savanna ecosystems reduced growth sensitivity to annual variation in precipitation relative to trees in a closed-canopy forest condition. Suppressed trees were also less responsive to climate variability than intermediate or co-dominant trees. Both annual wood and latewood growth were reduced by 21–33% the first year after prescribed fire for treatments with a 2- and 3-year fire return interval. Multiple regression combing temperature and precipitation variables as well as time since fire accounted for 55% of the variability in annual ring growth. Our findings indicate that a drier climate with hotter summers will likely reduce the growth of shortleaf pine growing at the western margin of its range while warmer temperatures in October, by extending the growing season, may help ameliorate the effects of warmer summers. Management to reduce stand density, either through thinning or by prescribed fire, may dampen some of the variation of growth in response to climate variability.
Arjun Adhikari; Ronald E. Masters; Henry Adams; Kumar P. Mainali; Chris B. Zou; Omkar Joshi; Rodney E. Will. Effects of climate variability and management on shortleaf pine radial growth across a forest-savanna continuum in a 34-year experiment. Forest Ecology and Management 2021, 491, 119125 .
AMA StyleArjun Adhikari, Ronald E. Masters, Henry Adams, Kumar P. Mainali, Chris B. Zou, Omkar Joshi, Rodney E. Will. Effects of climate variability and management on shortleaf pine radial growth across a forest-savanna continuum in a 34-year experiment. Forest Ecology and Management. 2021; 491 ():119125.
Chicago/Turabian StyleArjun Adhikari; Ronald E. Masters; Henry Adams; Kumar P. Mainali; Chris B. Zou; Omkar Joshi; Rodney E. Will. 2021. "Effects of climate variability and management on shortleaf pine radial growth across a forest-savanna continuum in a 34-year experiment." Forest Ecology and Management 491, no. : 119125.
The recently published article contained several errors in Table 3. The corrected table is provided here.
Arjun Adhikari; Lisa J. Rew; Kumar P. Mainali; Subodh Adhikari; Bruce D. Maxwell. Correction to: Future distribution of invasive weed species across the major road network in the state of Montana, USA. Regional Environmental Change 2020, 20, 1 -2.
AMA StyleArjun Adhikari, Lisa J. Rew, Kumar P. Mainali, Subodh Adhikari, Bruce D. Maxwell. Correction to: Future distribution of invasive weed species across the major road network in the state of Montana, USA. Regional Environmental Change. 2020; 20 (3):1-2.
Chicago/Turabian StyleArjun Adhikari; Lisa J. Rew; Kumar P. Mainali; Subodh Adhikari; Bruce D. Maxwell. 2020. "Correction to: Future distribution of invasive weed species across the major road network in the state of Montana, USA." Regional Environmental Change 20, no. 3: 1-2.
Invasive plant species are a significant global problem, with the potential to alter structure and function of ecosystems and cause economic damage to managed landscapes. An effective course of action to reduce the spread of invasive plant species is to identify potential habitat incorporating changing climate scenarios. In this study, we used a suite of species distribution models (SDMs) to project habitat suitability of the eleven most abundant invasive weed species across road networks of Montana, USA, under current (2005) conditions and future (2040) projected climates. We found high agreement between different model predictions for most species. Among the environmental predictors, February minimum temperature, monthly precipitation, solar radiation, and December vapor pressure deficit accounted for the most variation in projecting habitat suitability for most of the invasive weed species. The model projected that habitat suitability along roadsides would expand for seven species ranging from + 5 to + 647% and decline for four species ranging from − 11 to − 88% under high representative concentration pathway (RCP 8.5) greenhouse gas (GHG) trajectory. When compared with current distribution, the ensemble model projected the highest expansion habitat suitability with six-fold increase for St. John’s Wort (Hypericum perforatum), whereas habitat suitability of leafy spurge (Euphorbia esula) was reduced by − 88%. Our study highlights the roadside areas that are currently most invaded by our eleven target species across 55 counties of Montana, and how this will change with climate. We conclude that the projected range shift of invasive weeds challenges the status quo, and requires greater investment in detection and monitoring to prevent expansion. Though our study focuses across road networks of a specific region, we expect our approach will be globally applicable as the predictions reflect fundamental ecological processes.
Arjun Adhikari; Lisa J. Rew; Kumar P. Mainali; Subodh Adhikari; Bruce D. Maxwell. Future distribution of invasive weed species across the major road network in the state of Montana, USA. Regional Environmental Change 2020, 20, 1 -14.
AMA StyleArjun Adhikari, Lisa J. Rew, Kumar P. Mainali, Subodh Adhikari, Bruce D. Maxwell. Future distribution of invasive weed species across the major road network in the state of Montana, USA. Regional Environmental Change. 2020; 20 (2):1-14.
Chicago/Turabian StyleArjun Adhikari; Lisa J. Rew; Kumar P. Mainali; Subodh Adhikari; Bruce D. Maxwell. 2020. "Future distribution of invasive weed species across the major road network in the state of Montana, USA." Regional Environmental Change 20, no. 2: 1-14.
The growth and distribution of plant species in water limited environments is often limited by the atmospheric evaporative demands which is measured in terms of potential evapotranspiration (PET). While PET estimated by different methods have been widely used to assess vegetation response to climate change, species distribution models offer unique opportunity to compare their efficiency in predicting habitat suitability of plant species. In this study, we perform the first multi-species comparison of two widely used metrics of PET i.e., Penman-Monteith and Thornthwaite, and show how they result in similar or different on projected distribution of water limited species and potential consequences on their conservation strategies across North Central U.S. To build species distribution models of eight species, we used two sets of environmental predictors which were identical except for the metric of PET (Penman-Monteith vs Thornthwaite) and projected habitat suitability for historical (2005) and future (2099) periods. We found an excellent model performance with no difference under two sets of predictors (AUC = ∼0.93). The relative influence of Thornthwaite PET on habitat prediction was higher than Penman PET for most of the species. We observed that the area of the projected suitable habitat was always higher under Thornthwaite set of predictors than Penman set of predictors (ranges from 25 % to 941 %), with the exception of Pinus contorta for which the reverse was true. In most cases, these differences were non-trivial, indicating that the choice of the PET metric, although both of them are commonly used, can have dramatic consequences on the conservation management decisions. Therefore, the conservation management decisions can be markedly different depending on the choice of the PET metric used for species distribution modeling of water limited species.
Arjun Adhikari; Kumar P. Mainali; Imtiaz Rangwala; Andrew J. Hansen. Various measures of potential evapotranspiration have species-specific impact on species distribution models. Ecological Modelling 2019, 414, 108836 .
AMA StyleArjun Adhikari, Kumar P. Mainali, Imtiaz Rangwala, Andrew J. Hansen. Various measures of potential evapotranspiration have species-specific impact on species distribution models. Ecological Modelling. 2019; 414 ():108836.
Chicago/Turabian StyleArjun Adhikari; Kumar P. Mainali; Imtiaz Rangwala; Andrew J. Hansen. 2019. "Various measures of potential evapotranspiration have species-specific impact on species distribution models." Ecological Modelling 414, no. : 108836.
Water balance influences the distribution, abundance, and diversity of plant species across Earth’s terrestrial system. In this study, we examine changes in the water balance and, consequently, the dryland extent across eight ecoregions of the north-central United States by quantifying changes in the growing season (May–September) moisture index (MI) by 2071–99, relative to 1980–2005, under three high-resolution (~4 km) downscaled climate projections (CNRM-CM5, CCSM4, and IPSL-CM5A-MR) of high-emission scenarios (RCP8.5). We find that all ecoregions are projected to become drier as based on significant decreases in MI, except four ecoregions under CNRM-CM5, which projects relatively more moderate warming and much greater increases in precipitation relative to the other two projections. The mean projected MI across the entire study area changes by from +4% to −33%. The proportion of dryland (MI < 0.65) is projected to increase under all projections, but more significantly under the warmer and drier projections represented by CCSM4 and IPSL-CM5A-MR; these two projections also show the largest spatial increases in the arid (33%–53%) and hyperarid (135%–180%) dryland classes and the greatest decrease in the dry subhumid (from −56% to −88%) dryland class. Among the ecoregions, those in the semiarid class have the highest increase in potential evapotranspiration, those in the nondryland and dry subhumid class have the largest decrease in MI, and those in the dry subhumid class have the greatest increase in dryland extent. These changes are expected to have important implications for agriculture, ecological function, biodiversity, vegetation dynamics, and hydrological budget.
Arjun Adhikari; Andrew J. Hansen; Imtiaz Rangwala. Ecological Water Stress under Projected Climate Change across Hydroclimate Gradients in the North-Central United States. Journal of Applied Meteorology and Climatology 2019, 58, 2103 -2114.
AMA StyleArjun Adhikari, Andrew J. Hansen, Imtiaz Rangwala. Ecological Water Stress under Projected Climate Change across Hydroclimate Gradients in the North-Central United States. Journal of Applied Meteorology and Climatology. 2019; 58 (9):2103-2114.
Chicago/Turabian StyleArjun Adhikari; Andrew J. Hansen; Imtiaz Rangwala. 2019. "Ecological Water Stress under Projected Climate Change across Hydroclimate Gradients in the North-Central United States." Journal of Applied Meteorology and Climatology 58, no. 9: 2103-2114.
Covering about 40% of Earth’s land surface and sustaining at least 38% of global population, drylands are key crop and animal production regions with high economic and social values. However, land use changes associated with industrialized agricultural managements are threatening the sustainability of these systems. While previous studies assessing the impacts of agricultural management systems on biodiversity and their services focused on more diversified mesic landscapes, there is a dearth of such research in highly simplified dryland agroecosystems. In this paper, we 1) summarize previous research on the effects of farm management systems and agricultural expansion on biodiversity and biodiversity-based ecosystem services, 2) present four case studies assessing the impacts of management systems on biodiversity and ecosystem services across highly simplified dryland landscapes of the Northern Great Plains (NGP), USA, 3) discuss approaches to sustain biodiversity-based ecosystem services in drylands, and 4) present a conceptual framework for enhancing agricultural sustainability in the drylands through research, policy, economic valuation, and adaptive management. An analysis of the land use changes due to agricultural expansion within the Golden Triangle, a representative agricultural area in the NGP, indicated that the proportion of land conversion to agriculture area was 84%, 8%, and 7% from grassland, riparian, and shrubland habitats, respectively. Our results showed this simplification was associated with a potential reduction of pollination services. Also, our economic analysis projected that if 30% parasitism could be achieved through better management systems, the estimated potential economic returns to pest regulation services through parasitoids in Montana, USA alone could reach about $11.23 million. Overall, while dryland agroecosystems showed a significant loss of native biodiversity and its services, greater pest incidence, and a decrease in plant pollinator networks, these trends were moderately reversed in organically managed farming systems. In conclusion, although land use changes due to agricultural expansion and industrialized farming threaten the sustainability of dryland agroecosystems, this impact can be partially offset by coupling ecologically-based farming practices with adaptive management strategies.
Subodh Adhikari; Arjun Adhikari; David Weaver; Anton Bekkerman; Fabian Menalled. Impacts of Agricultural Management Systems on Biodiversity and Ecosystem Services in Highly Simplified Dryland Landscapes. Sustainability 2019, 11, 3223 .
AMA StyleSubodh Adhikari, Arjun Adhikari, David Weaver, Anton Bekkerman, Fabian Menalled. Impacts of Agricultural Management Systems on Biodiversity and Ecosystem Services in Highly Simplified Dryland Landscapes. Sustainability. 2019; 11 (11):3223.
Chicago/Turabian StyleSubodh Adhikari; Arjun Adhikari; David Weaver; Anton Bekkerman; Fabian Menalled. 2019. "Impacts of Agricultural Management Systems on Biodiversity and Ecosystem Services in Highly Simplified Dryland Landscapes." Sustainability 11, no. 11: 3223.
The remaining wildlands in the North Central US include varying proportions of public, private, and tribal lands across water balance ecotones. These wildlands may be highly vulnerable changing climate impacting their ability to sustain biodiversity and ecosystem functioning. We quantified projected changes in growing season climate (temperature) and water balance (MI: moisture index) in Greater Wildland Ecosystems (GWEs) and land allocation types (public, private, and tribal lands) across Central Plains, Western Plains, and Western Mountains ecoregions of North Central US by using high-resolution climate data from GCM output of 1980–2005 to 2071–2099. We also tested for the evidence of systematic climatic bias on tribal lands, which are often claimed to be distributed non-randomly. We found that the historic temperature was lower for Western Mountains compared to Western and Central Plains’ GWEs. The climate model projected drier and warmer GWEs with a narrow difference in increased temperature (4.6 to 5.5 °C). The MI was projected to have the greatest decrease in Central Plains (− 28%) and the least in Western Plains (− -17%) GWEs. Our findings revealed that the GWEs and land allocation types are increasingly vulnerable to changing climate. We conclude that the distribution of tribal and public lands is not climatically biased in the historic period and the projected rates of change in climate are similar among land allocation types within each GWE. All GWEs, however, are projected to warm and undergo increasing aridity, which may challenge management to sustain ecological health and human wellbeing across all land allocation types.
Arjun Adhikari; Andrew J. Hansen. Climate and water balance change among public, private, and tribal lands within Greater Wild land Ecosystems across North Central USA. Climatic Change 2019, 152, 551 -567.
AMA StyleArjun Adhikari, Andrew J. Hansen. Climate and water balance change among public, private, and tribal lands within Greater Wild land Ecosystems across North Central USA. Climatic Change. 2019; 152 (3-4):551-567.
Chicago/Turabian StyleArjun Adhikari; Andrew J. Hansen. 2019. "Climate and water balance change among public, private, and tribal lands within Greater Wild land Ecosystems across North Central USA." Climatic Change 152, no. 3-4: 551-567.